CD95 Ligand expression enhances growth of murine renal cell carcinoma in vivo

The CD95/CD95 ligand (CD95L)system plays an important role in the induction of lymphoid apoptosis and has been implicated in the suppression of immune responses. In this system, two murine CD95L-transfected renca clones and a control renca clone transfected only with the vector were implanted into t he subcapsule of the left kidney of Balb/c and Balb/c nude mice. Both CD95L -expressing and control renca clones formed macroscopic tumors in all of th e Balb/c and Balb/c nude hosts 14 days after implantation. Growth of tumors of murine CD95L-transfected renca cells was significantly better than that of control renca cells in Balb/c mice, while the growth advantage of CD95L transfectants was not observed in Balb/c nude mice. Lymphocytes underwent apoptosis mainly in the periphery of the CD95L-expressing tumors but not in control tumors grown in Balb/c mice, while lymphocytes undergoing apoptosi s were not observed in CD95L-expressing tumors or in control tumors grown i n Balb/c nude mice. Neutrophilic recruitment was rarely observed in CD95L-e xpressing or control tumors. CD95L ex; pressed on renca cells possibly supp ressed immune responses against renca tumors by inducing apoptosis of the i nfiltrating lymphocytes. However, CD95L-expressing renca cells did not form tumors in the renal subcapsule of allogeneic C3H/HeJ mice.